The present invention relates generally to Local Area Networks ("LANS") and more specifically to an improved attachment unit interface (AUI) for implementation of communication protocols in a LAN system.
The incorporated patents and patent applications describe a set of inventions that relate to devices that facilitate implementation of local area networks. It is one aspect of those disclosures to describe implementation of various IEEE standards, including 802.3 and 10 Base T, both hereby expressly incorporated by reference for all purposes. These documents include a description of an attachment unit interface (AUI) used in one common implementation of a carrier sense, multiple access/collision detection (CSMA/CD) network protocol. One common implementation of this CSMA/CD protocol is the well-known ETHERNET protocol.
FIG. 1 illustrates one common implementation of a typical AUI 10 to communicate between a repeater data terminal equipment (DTE) 12 implemented as part of a repeater 14, for example, and a transceiver DTE 16, implemented as part of a medium attachment unit (MAU) 18, for example. As illustrated, AUI 10 traditionally includes three differential signals, a Data Out (DO), a Data In (DI), and a Control In (CI). An AUI driver 30 transmits one differential signal to an AUI receiver 32.
Repeater DTE 12 has one AUI driver 30 and two AUI receivers 32. MAU DTE 16 has two AUI drivers 30 and one AUI receiver 32. The AUI driver illustrated in the incorporated patents and patent application satisfactorily implements the necessary communications and signalling functions as described in detail therein.
FIG. 2 is an illustration of an AUI driver cell 100 described in detail in the incorporated references. Driver cell 100 includes a controller 102 for controlling a pair of MOS current drivers (transistors Q.sub.1 -Q.sub.4), an end-of-transmission delimiter (ETD) transistor Q.sub.5, and a terminating resistor R. Controller 102 includes appropriate logic structures to implement the logic function illustrated by Table I below.
TABLE I ______________________________________ SI.sup.+ SI.sup.- MNCV W X Y Z N TR.sup.+ TR.sup.- ______________________________________ 1 0 1 1 0 1 0 1 1 0 0 1 1 0 1 0 1 1 0 1 1 0 0 0 0 1 1 0 * * 0 1 0 0 0 1 1 0 * * ______________________________________ *Termination of ETD, all transistors are on.
AUI driver cell 100 may be integrated into a semiconductor device defining repeater 14 or MAU 18. Thus, repeater 14 includes a single AUI line driver cell 100 for each AUI 10. Due to proliferation of network management tools, it may be desirable in some instances to have use of a MAU DTE in repeater 14. A simple, but inefficient solution would be to simply provide for two AUI 10, one configured for a MAU DTE and one configured for a repeater DTE, each having six pins. In some implementations, there can be twelve AUI 10 per repeater 14, resulting in a requirement for an extra seventy-two pins if every port were to be reconfigurable.
It is an object of the present invention to provide a more efficient solution to the problem of permitting a reconfiguration of a MAU DTE to a repeater DTE, and vice-versa.